AUTORADIOGRAPHY WITH SATURATION EXPERIMENTS OF C-11 RO-15-1788 BINDING TO HUMAN BRAIN SECTIONS

In vitro autoradiography of a C-11-labelled ligand, Ro 15-1788, was used in saturation experiments in order to quantify benzodiazepine receptor binding in whole human brain hemisphere cryo-sections. A special incubation chamber was developed with the aim of performing standardized quantitative studies with short-lived positron emitting isotopes. C-11-labelled ligand binding was studied in temporal cortex, cerebellum, white matter and pons incubated in vitro. White matter, lacking benzodiazepine receptor binding, was used as an estimate of nonspecific binding, for calculation of specific binding. Saturability of binding was demonstrated in the neocortical and cerebellar regions. Radioactivity counting of incubated adjacent tissue sections was done as a control. Computerized densitometry of the autoradiograms gave similar results as the tissue counting. A comparison with in vivo saturation experiments using the same C-11-labelled ligand and positron emission tomography in healthy human subjects also gave binding characteristics of the same magnitude. The C-11-autoradiograms showed a good spatial resolution (about 180-mu-m). C-11-autoradiography with suitable radioligands should be a valuable technique of screening the distribution and characteristics of neuroreceptors in the human brain. This quantitative method will provide the PET investigator with preliminary binding data, and may thus supply valuable information concerning positioning in PET and concerning significant regions of interest.